1. Field of the Invention
The present invention relates to a waveform generating device in which a musical tone is reproduced by reading out a plurality of waveform data of separated segments in accordance with performance data and, in particular, to a waveform generating device with which, in those cases where there has been an alteration of the performance tempo during the performance, waveform data may be compressed or expanded on the time axis in real time in conformance with the tempo alteration.
2. Description of Related Art
In conventional waveform generating devices, waveform data that have syllables are stored in the storage means and in those cases where the user implements a reproduction instruction such that one syllable of the waveform data is prolonged, the reproduction time is prolonged in real time by establishing a loop reproduction segment in the end of the waveform data that correspond to the syllable for which the prolongation instruction has been made and carrying out loop reproduction in the waveform generation means. In addition, in those cases where a sound production instruction has been made such that the sound production of one syllable in the waveform data is shortened, the shortening of the reproduction time is carried out in real time by interrupting the reproduction of the syllable that is currently being produced in the waveform generation means and shifting the reproduction position toward the head of the waveform data that correspond to the next syllable.
With such conventional waveform generating devices, if the reproduction instruction is repeated, the reproduction of the appropriate audio phrase is begun and sound production that corresponds to the reproduction instruction time is possible. However, due to the fact that a loop reproduction is done only of the end of the syllable for which a prolongation instruction has been issued, there has been the weakness that the feeling of disorder given to the user is great. In addition, in those cases where a shortening instruction has been issued for a single syllable, since the syllable is reproduced no further than the middle, a musical tone that gives a feeling of disorder is reproduced. In those cases also where a portamento performance is done, since the pitch or volume cannot be altered until the next reproduction instruction (for example, pressing a key) is given, the feeling of disorder imparted to the user has been great.
Our prior art of Japanese Unexamined Patent Application Publication (Kokai) Number Hei 10-260685 (Patent Reference 1) discloses a sound source for compressing or expanding waveform data on the time axis (hereinafter, referred to as an “audio phrase sound source”). The audio phrase sound source disclosed in Patent Reference 1 carries out the compression processing or the expansion processing of the waveform data on the time axis by supplying time compression and expansion percentage information (the information that indicates the percentage that the waveform data are to be compressed or expanded on the time axis) and pitch information as parameters to a DSP (digital signal processor) from a CPU (central processing unit).
FIG. 1 is a conceptual block diagram of the audio phrase sound source disclosed in Patent Reference 1. In accordance with FIG. 1, the audio phrase sound source of Patent Reference 1 is furnished with at least storage means with which the waveform data are stored and waveform generation means (a portion of the DSP) with which the output waveform generation processing is performed based on the time compression and expansion percentage information and the pitch information that are supplied from the CPU for the waveform data that are input from the storage means.
The present invention was devised taking into consideration the above-mentioned prior art. The purpose thereof is to provide a waveform generation device that, when carrying out compression or expansion on a time axis of waveform data that has syllables and that utilizes technology employed in a sound source, can arbitrarily carry out in real time control the compression or expansion on a time axis of waveform data and control of the pitch, as shown in the above-mentioned audio phrase sound source, and makes possible the playback of all syllables so as to not impart a sense of incongruity to a user.
Furthermore, the purpose of the present invention is to provide a waveform generation device devised that, in the case of portamento performance and the like that utilizes technology employed in a sound source, can arbitrarily carry out in real time control the compression or expansion on a time axis of waveform data and control of the pitch, as shown in the above-mentioned audio phrase sound source, and makes possible the commencement of a change of the pitch and volume without waiting for the playback instructions of the next pressed key and the like, so as to not impart a sense of incongruity to a user.